Showing papers on "Transverse plane published in 1996"

A cadaveric study of the anatomy and stability of the distal radioulnar joint in the coronal and transverse planes

Abstract: Fifty preserved cadaver wrist specimens were studied. The anatomy of the distal radioulnar joint is complex, with varying configurations in the transverse and midcoronal planes. There is disparity in the radii of curvature of the sigmoid notch and the ulna-articular surface in the transverse plane, with resultant articular incongruity. Motion at the distal radioulnar joint is, hence, likely to be a combination of sliding and rotation with a small area of true appositional contact. The palmar osteocartilaginous lip of the sigmoid notch, along with the interosseous membrane, may be of importance in distal radioulnar stability. Palmar and dorsal radioulnar ligaments may act as “check-rein” ligaments, especially when seen with the “flat face” (type A) sigmoid notch.

Plasma Response to Strongly Sheared Flow.

Abstract: Laboratory observations of reactively driven plasma waves in the ion-cyclotron frequency range associated with a localized, transverse dc electric field are reported This wave excitation occurs even when the field-aligned current is negligible, a situation often reported in the space plasma environment The fluctuation spectrum is broadband in frequency and its peak depends on the magnitude of the dc electric field Comparison with theory indicates that these waves result from a strong inhomogeneity in the energy density caused by sheared E 3 B flow [S0031-9007(96)01143-X]

Stent mounting device

Abstract: A stent mounting device and method of using the device comprising a disposable device for holding a stent, into which a delivery system such as a balloon catheter can be inserted, and the stent crimped onto the delivery system, after which the delivery system and mounted stent are removed from the device. A stent is carried in a channel formed by four corner segments of four co-axillay arranged spaced blocks. Two adjacent blocks are elastically mounted in each of two parallel, opposed, cooperating actuators. The corner segments form an elongated channel sized to retain a conventional stent. Two elastic rods are placed between opposite blocks in opposite actuators. When the actuators are pressed together the rods are deformed to provide pressure transverse to the line of pressure, so that the cross sectional area of the channel is decreased in both directions, crimping the stent uniformly onto a delivery system.

A new approach to measuring transverse properties of structural tubing by a ring test

Abstract: A new approach to the ring test is presented in this paper. Three-dimensional elastoplastic finite element modeling with contact has been performed to analyze the stress and strain distribution in the ring, to optimize the ring testing system, and to investigate the effect of friction between the ring specimen and the fixture. Based on the numerical results, a new design of a holding device that creates a uniaxially stressed zone is proposed in order to determine transverse behavior of tubular products, such as the modulus and the stress-strain curve. A case study is presented on nuclear cladding tubes in Zircaloy. The approach shows promise for testing various kinds of materials in structural tubing, including ductile or brittle materials, metals, composites, or polymers.

Dispersive properties of a magnetized plasma with a field‐aligned drift and inhomogeneous transverse flow

Abstract: Electrostatic fluctuations driven by the combination of a magnetic‐field‐aligned electron current and a localized transverse electric field are investigated. Characteristic parameters, such as scale length and magnitude of the sheared E×B velocity, magnitude of the magnetic‐field‐aligned current, and temperature ratio τ≡Ti/Te are varied to include conditions associated with electrostatic waves driven entirely by magnetic‐field‐aligned current, driven entirely by transverse electric field, and driven by a combination of magnetic‐field‐aligned current and transverse electric field. It is shown that, in contrast to the homogeneous case of current‐driven modes, the modes in the presence of a transverse‐velocity shear can be unstable in a wider range of temperature ratio τ and they are broadband in frequency. Using a simplified model, numerical solutions of the nonlocal dispersion relation, and physical arguments, cases of stabilization and destabilization due to the inhomogeneous energy‐density driven instabi...

The influence of tangential mean flow on the rayleigh conductivity of an aperture

Abstract: An investigation is made of the influence of grazing mean flow on the Rayleigh conductivity of an aperture in a thin rigid plane. The fluid is assumed to be incompressible and inviscid, but the Kutta condition is applied to permit the generation of vorticity at the edge of the aperture by an applied time-varying pressure field. Numerical results are given for a circular aperture in the two cases of (i) one-sided mean flow, when the aperture is spanned by a plane vortex sheet in the undisturbed state, and (ii) two-sided mean flow, when the mean velocity is the same on both sides of the plane, so that the undisturbed motion is irrotational. In both cases there exist frequency ranges within which perturbation energy is either absorbed or generated by the mean flow. The numerical results are supplemented by an approximate analytical treatment of the same problem for a rectangular aperture of large aspect ratio (with its long edge transverse to the mean flow direction). The aperture flux for one-sided flow is shown to be absolutely unstable, and may in principle be triggered by an arbitrary, small disturbance in the mean stream. For two-sided flow the motion is conditionally unstable, in the sense that perturbations are amplified by the extraction of energy from the mean flow only when the frequency of the applied pressure lies in certain discrete bands.

Transverse-mode control of vertical-cavity surface-emitting lasers

Abstract: Transverse-mode control of vertical-cavity surface-emitting lasers (VCSELs) has been investigated A theoretical model takes into account the distributions of carriers, optical field, and temperature Using a method of finding self-consistent solutions for the carrier diffusion, optical field, and thermal conduction equations, we have studied the influence of current spreading, injected current density, gain-guided aperture, and window diameter on the transverse modes The calculated results agree well with those of experiments and show that the transverse-mode evolution of VCSELs depends on the changes of gain and refractive index induced by carriers and heating; decreasing temperature rise and profile width, current spreading, and gain-guided aperture dimension, increasing homogeneity of the injected carriers at the lasing region, and decreasing window diameter are effective methods to suppress high-order transverse modes

Longitudinal and transverse effects of nonspecular reflection

Abstract: A rigorous spectral analysis is given for the nonspecular reflection of a three-dimensional Gaussian beam at a dielectric isotropic planar structure. For the first time all independent nonspecular effects are derived in a self-consistent manner for the three-dimensional case. It is shown that the longitudinal nonspecular effects in the incidence plane, that is, the lateral and focal shifts of the beam waist position, the angular rotation of the reflected-beam axis, and the modifications of the beam waist width and complex amplitude, have their direct analogies in the plane transverse to the incidence and interface planes that gives transverse nonspecular effects. Moreover, the existence of the other, not yet reported, effect of nonspecular modification of the beam polarization is also proved. A role for TM and TE polarizations in reflected-beam formation is indicated. The results show that, up to the symmetric second-order terms in approximation of Fresnel coefficients, each of the longitudinal and transverse beam factors independently preserves its shape under reflection at the expense of changes of the beam reference frame, width, amplitude, and polarization parameters.

A Higher-Order Theory for Vibration of Doubly Curved Shallow Shells

Abstract: A higher-order shear deformation 'theory is presented for vibration analysis of thick, doubly curved shallow shells. An orthogonal curvilinear coordinate system is em- ployed to arrive at the strain components. A third-order displacement field in trans- verse coordinate is adopted. Though no transverse normal stress is assumed, the theory accounts for cubic distribution of the transverse shear strains through the shell thickness in contrast with existing parabolic shear distribution. The unsymmetric shear distribution is a physical consequence of the presence of shell curvatures where the stress and strain of a point above the mid-surface are different from its counterpart below the mid-surface. Imposing the vanishing of transverse shear strains on top and bottom surfaces, the rotation field is reduced from a six-degree to a two-degree system. The discrepancy between the existing and the present theories is highlighted.

Trunk kinematics of one-handed lifting, and the effects of asymmetry and load weight

Abstract: This study investigated trunk kinematic differences between lifts performed using either one hand (unsupported) or two hands. These effects were studied while beginning the lifts from different asymmetric starting positions and while lifting different load weights. Each subject lifted a box from a lower to an upper platform under one- and two-handed lifting conditions. Subjects wore a lumbar spine electrogoniometer, from which relative motion components were calculated in the trunk's three cardinal planes. Results of this study showed that one-handed lifting resulted in significantly higher ranges of motion in the lateral and transverse planes and greater flexion in the sagittal plane. Back motion characteristics previously found to be associated with low back disorders were all significantly higher for one-handed lifts. The two-handed lift technique, on the other hand, produced overall faster trunk motions in the sagittal plane and equal or larger acceleration and deceleration magnitudes in all planes of motion. Increases in load asymmetry affected trunk kinematics, in that magnitude values for range of motion, velocity and acceleration became much greater with increasingly asymmetric load positions. Increasing the load weight appeared to have less of an effect on trunk kinematics, with increases in position mostly occurring during sagittal and lateral bending. These results suggest that unsupported one-handed lifting loads the spine more than two-handed lifts, due to the added coupling. Applying these results to a previously developed model, one-handed lifting was also found to increase one's risk of suffering a low back disorder.

Wood joining biscuits with centering feature

Abstract: A carpentry biscuit is provided having an elongated planar body formed of wood having opposed faces spaced apart and thickness T. One of the opposed faces is provided with a longitudinal alignment mark oriented along a longitudinal axis and a transverse alignment mark aligned perpendicular to the transverse axis to aid the user in positioning the biscuit in a slot formed in a pair of boards to be joined together.

Hourly variances of fluctuations in the heliospheric magnetic field out of the ecliptic plane

Abstract: Magnetic field fluctuations at high heliographic latitudes are discussed in terms of the latitude and radial dependence of their variances, as observed by the Ulysses spacecraft. The increased level of transverse fluctuations in fast solar wind flows from the polar coronal holes is similar to that found in high speed streams near the ecliptic. However, continuous observations in the fast solar wind both southward and northward of the solar equatorial plane has allowed the determination of the radial dependence of fluctuations on hourly and shorter timescales, free from additional energy input from stream-stream interactions or from coronal mass ejections and in the presence of a slowly evolving, low frequency Alfvenic population. The conclusion is that fluctuations in the inertial range in the homogeneous polar coronal flows decay faster than predicted by the WKB approximation. However, even minor compression effects can increase the energy in these fluctuations.

On the Landau damping and decoherence of transverse dipole oscillations in colliding beams

Abstract: Coherent transverse dipole oscillations in colliding head-on non-rigid bunches are studied using the Vlasov equation. The corresponding eigenvalue problem is solved numerically in the case of round Gaussian bunches of equal size but with not necessarily equal intensities. Transition from the weak-strong to the strong-strong cases is found at the intensity ratio of about 600/0 when a discrete 1r-mode frequency emerges from continuum of eigenfrequencies related to the beam-beam tunespread in the weaker bunch. In the strong-strong case the large coherent beam-beam tuneshift dominates over interchange processes between coherent and incoherent motion; it can switch off Landau damping of dipole transverse oscillations, slows down incoherent emittance growth due to external kicks on the beams. The consequences for the transverse feedback operation in collision arc discussed.

Simultaneous observation of electric field coupling to longitudinal and transverse ferroelectricity in a chiral liquid crystal

Abstract: We report novel odd-even layering effects in freely suspended films of the chiral liquid crystal MHPOBC in its antiferroelectric smectic phase. Films with an odd number of smectic layers are characterized by transverse ferroelectricity (molecular tilt plane perpendicular to applied electric field E), while films with an even number of layers exhibit longitudinal ferroelectricity (molecular tilt plane parallel to E). This is the first observation of the simultaneous electric field manipulation of longitudinal and transverse ferroelectric polarization in liquid crystals.

External cavity micro laser apparatus

Abstract: External cavity micro laser apparatus comprises at least one multimode micro laser having an emission aperture with a relatively long dimension lying in a slow axis plane and a relatively short dimension lying in a fast axis plane. The laser produces multiple transverse lasing modes, the multiple modes having multiple lasing lobe components. External cavity means embracing the laser has an output section including spatial filter means, which may be the input aperture of an optical waveguide, for effectively selecting at least one of the transverse lasing lobe components. The cavity output section includes imaging means for imaging at the spatial filter means a far field spatial frequency distribution in the slow axis plane of the emission aperture, at which distribution the lasing lobe components are spatially distinguishable. The cavity output section also includes feedback means for causing a fraction of the optical energy in the selected lasing lobe component(s) to be fed back to the laser for amplification by the laser. A cavity return section receives the amplified lasing lobe component after reflection from the laser. Return means in the return section efficiently returns to the laser means at least a portion of the amplified and reflected lasing lobe component.

Improvement of cardiac imaging in electrical impedance tomography by means of a new electrode configuration

Abstract: Until now, electrical impedance tomography (EIT) has been used for cardiac imaging with the electrodes attached transversally at the level of the fourth intercostal space at the anterior side. However, the results obtained with this electrode configuration have been disappointing. The aim of the present study was to improve the measurement design of EIT for cardiac imaging. Therefore, magnetic resonance imaging (MRI) scans were analysed in two healthy subjects to determine the optimum anatomical plane in which atria and ventricles are clearly visually separated. From these findings, we proposed a new oblique plane at the level of the ictus cordis anteriorly and 10 cm higher posteriorly. EIT pictures obtained in the oblique plane revealed a better visual separation between the ventricles and atria than with the electrodes attached in the transverse plane. Comparison between volume changes measured by means of MRI and impedance changes in different regions of interest measured with EIT were performed with the electrodes in the proposed oblique plane. Ventricular and atrial volume changes measured by MRI show the same pattern as do impedance changes measured by EIT. Furthermore, we assessed the reproducibility and validity of the oblique electrode configuration in ten healthy mate volunteers during rest and during exercise compared with the currently used transverse electrode configuration. The reproducibility coefficient assessed from repeated measurements with the electrodes attached in the oblique plane was 0.98 at rest and 0.85 during exercise. For the transverse plane the reproducibility coefficient was 0.96 at rest and 0.66 during exercise. The well-known increase in stroke volume during exercise is 40% in healthy subjects. The increase in impedance change during exercise compared with rest was 34 +/- 13% (20-59%) for the oblique plane and 68 +/- 57% (13-140%) for the transverse plane. From these results we infer that the stroke volume is assessed more accurately by using the oblique plane. From these findings, we conclude that the oblique plane improved the cardiac measurements, because (i) a better spatial separation of the heart compartments is obtained, (ii) the results are more reliable and (iii) measurements during exercise are more accurate with the electrodes attached in an oblique plane.

Computational Model for Reinforcing Bar Embedded in Concrete under Combined Axial Pullout and Transverse Displacement.

Abstract: An enhanced computational model for the prediction of reinforcing bar behavior under the generic condition of axial pullout and transverse displacement is presented. Based on the compatibility relationship between the transverse displacement and the curvature induced in the embedded bar, the localized phenomenon of the bar close to the interface is formulated, and its formulation makes it possible to express the reduced pullout stiffness of embedded bars encountered under combined axial pullout and transverse dowel action.

Transverse mode competition in a CO2 laser.

Abstract: Transverse patterns in lasers have been observed since the earliest days of laser physics, as, e.g., in 1964 when they were reported for the first time on the transverse structures of a HeNe laser @1#, but transverse dynamics studies developed only in the past decade. Two approaches have been followed, depending essentially on the number of transverse degrees of freedom of the system, i.e., on the Fresnel number. At low Fresnel number, it has been shown that modal expansion of the field on a suitable basis of empty cavity modes is well adapted to explain the main properties of the various stationary and dynamical regimes @2,3#. At high Fresnel number, Coullet et al. demonstrated theoretically the existence of optical turbulence induced by defects, also called optical vortices, and suggested describing complex spatiotemporal dynamics as a function of such vortices @4#. Unfortunately, although phase singularities similar to optical vortices are common in the transverse patterns of lasers, and may form complex disordered patterns @3,5‐8#, optical turbulence in lasers has not yet been experimentally evidenced. Complex patterns have also been observed in a liquid-crystal device with optical feedback @9#, and turbulence has been evidenced in optical oscillators with photorefractive gain @10#. In CO 2 lasers, the limiting factor of the experimental analysis is the detection, as there is no technical solution to record patterns at a cadence of 1 MHz or higher, which is the typical scale of the dynamics. Therefore, the observations on laser transverse patterns are limited to the time averaged intensity @8#. The preliminary results of @8# showed that among a wide variety of patterns, the transverse profile of the CO 2 laser could exhibit self-organization, even at Fresnel numbers as large as 40. We show in this paper that in this situation, it is still possible to describe experimentally the patterns as a function of the modes of the empty cavity. Such an analysis allows us to evidence that patterns are combinations of a few modes among those present in the gain profile. The selection mechanism is shown to be transverse spatial hole burning, in good agreement with recent theoretical studies @11#. These results provide an alternative interpretation of laser patterns to that given by Feng et al. in terms of standing waves @12#. The experimental setup is essentially the one described in @8#. The detection consists in phosphorescent plates and a video camera. Unfortunately, as this system has a low resolution and is nonlinear, it provides pattern intensity distributions with a typical uncertainty of 20%. Another important point is the presence in the cavity of Brewster windows introducing astigmatism. This induces that ~i! the cylindrical symmetry of the cavity is broken to a rectangular symmetry, so that the Hermite-Gauss basis TEM m,n becomes relevant, and ~ii! the frequency degeneracy of modes having the same q5m1n index is lifted. Pertinent parameters to characterize the cavity are the generalized Fresnel number N F and the ratio Rn of the free spectral range to the transverse mode spacing. The former is a measure of the transverse degrees of freedom and the latter rules the interactions between the transverse modes. In @8#, it was shown that for Rn’15 and values of N F up to 30, the laser exhibits ordered time averaged intensity patterns @Figs. 1~a!‐~c!# with the following properties: ~i! patterns may be described as lattices of dark

Nonergodic Solute Transport in Three-Dimensional Heterogeneous Isotropic Aquifers

Abstract: The general expressions for the time-dependent ensemble averages of the second spatial moments ^A&and the effective dispersivities g, defined as (1/2m)(d^A&/dt) where mis the magnitude of the meanflow velocity m, are evaluated in order to study the effect of initial plume size on ^A&and gin three-dimensional heterogeneous isotropic aquifers under thefirst-order approximation to the particle displacement. The results confirm previousfindings that ^A&and ggenerally approach their respective ergodic limits Xand aas the size of a source increases, whereXand aare the single particle displacement covariance and the associated dispersivity, and that the transverse lengths of a source are more important than the longitudinal length for the ergodic condition to be met. The longitudinal dispersion of a nonergodic plume becomes Fickian or the effective asymptotic longitudinal dispersivity is constant at late time as long as one of the initial lateral lengths of the plume is nonzero, while the transverse dispersion is always non- Fickian and the effective asymptotic transverse dispersivities are always zero regardless of the initial plume size. The most important and interestingfindings are, when the longitudinal lengthl1 of an initial plume is larger than the lateral lengthsl2 andl3, both effective longitudinal and transverse dispersivities gii(i 51, 2, 3) increase to their respective peaks at early time, then g11decreases toward an asymptotic constant, whose value depends on the values of l2 and l3 (g113 0i f l 2 5 l 3 50), whereas g22 and g33 decrease to below zero (i.e., become negative), increase again, andfinally approach zero independent of the lateral lengths of the source. Comparison of the current study with a numerical simulation shows good agreement between the calculated and simulated longitudinal second spatial moments.

Blurring of vessels in spiral CT angiography: effects of collimation width, pitch, viewing plane, and windowing in maximum intensity projection.

Abstract: Purpose Our goal was to examine the effects of collimation width (CW), pitch, viewing plane, and windowing on the display of in-plane vessels in maximum intensity projection (MIP). Method A theoretical concept based on partial volume averaging of vessels was developed to describe the contents of voxels (densities) in MIP and to derive cross-sectional vessel diameters and blurring. To validate the concept and to describe the influence of pitch, a Plexiglas cone submerged in water was scanned with varying CW and pitch. Binary MIP with three representative window levels was chosen so that definitive vessel diameters could be quantitated. Results The theoretical concept correctly predicted voxel contents and blurring for CW > or = 3 mm and low pitch. For high pitch, actual blurring was larger; however, for a given table speed, blurring of the cone decreased with pitch while increasing with CW. Overall blurring was most effectively reduced by using a thin CW and the transverse viewing plane. In the transverse viewing plane, the least blurring was found using binary MIP with a low window level. On the contrary, in the longitudinal viewing plane, blurring was minimized using a window level halfway between the density of the cone and that of the surrounding water. Conclusion For CW > or = 3 mm, blurring of in-plane vessels can be explained with a simple geometrical concept based on partial volume. For accurate display, the transverse viewing plane should be used, a proper windowing must be chosen, and the CW should be kept below vessel size while raising the pitch to cover a reasonable volume.

Vortex fluid meter incorporating a double obstacle

Abstract: A vortex fluid meter (1) includes a pipe portion (2) of constant inside diameter in which the fluid flows, at least two obstacles disposed in the middle of the flow of the fluid in said pipe portion (2) each having a generally elongate shape with longitudinal and transverse dimensions perpendicular to the direction of flow of the fluid, and adapted to generate oscillatory fluid vortices, an upstream obstacle (4) having a substantially uniform trapezoidal transverse section and a downstream obstacle (6) having a generally T-shape transverse section, and means (10, 12, 14) for detecting the signal corresponding to the oscillations of said vortices and for deducing therefrom the fluid volume or flowrate.

Optical scanning system with diffractive optics

Abstract: An improved optical system having diffractive optic elements is provided for scanning a beam. This optical system includes a laser source for emitting a laser beam along a first path. A deflector, such as a rotating polygonal mirror, intersects the first path and translates the beam into a scanning beam which moves along a second path in a scan plane. A lens system (F-θ lens) in the second path has first and second elements for focusing the scanning beam onto an image plane transverse to the scan plane. The first and second elements each have a cylindrical, non-toric lens. One or both of the first and second elements also provide a diffractive element, which provides not only astigmatic correction, but may further provide chromatic aberration correction of the scanning beam. This astigmatic correction is achieved without the presence of any lens having a toroidal (toric) surface. The system may further have a third element in the first path of the beam prior to the deflector. This third element provides a lens having another diffractive element. This diffractive element can correct chromatic and spherical aberration of the scanning beam in the cross-scan plane, a plane perpendicular to the scan plane.

High-transverse-curvature tire, in particular for a two-wheeled vehicle

Abstract: A front tire for two-wheeled vehicles comprising a carcass of toric form having a high transverse curvature and provided with a central crown and two sidewalls terminating in a pair of beads for anchoring to a corresponding mounting rim, a tread band located on the crown and a circumferentially-inextensible belt structure disposed between the carcass and tread band. The belt structure at a radially external position is comprised of a layer of cord coils substantially disposed at a zero angle to the equatorial plane of the tire in axial side-by-side relationship and extended from one axial extremity of the belt to the other axial extremity of the belt. The winding thickness of the cord coils increasingly grows from the equatorial plane to the belt axial extremities.

Simplified conditions and configurations for phase-contrast imaging with hard x-rays

Abstract: A method of obtaining an image of a boundary of an object, the boundary representing a refractive index variation, the method including irradiating the boundary with penetrating radiation having high lateral spatial coherence and a propagation component transverse to the refraction index variation, and receiving at least a portion of the radiation on an image plane so as to form the image, the radiation having been refracted by the boundary such that the boundary is represented on the image by a corresponding intensity variation.